CONSOLIDATED STATEMENTS OF STOCKHOLDERS' EQUITY (USD $) In Thousands, except Share data, unless otherwise specified	Common Stock	Capital in Excess of Par Value	Retained Earnings	Accumulated Other Comprehensive Income (Loss)	Total
Balance at Dec. 31, 2009	$ 14,754	$ 2,720	$ 401,055	$ (8,806)	$ 409,723
Balance (in shares) at Dec. 31, 2009	147,547,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for stock incentive plans, net	59	4,889			4,948
Stock issued for stock incentive plans, net (in shares)	587,000
Stock purchased and retired	(14)	(832)	(949)		(1,795)
Stock purchased and retired (in shares)	(144,000)
Net income			146,742		146,742
Pension adjustment, net of taxes				(1,350)	(1,350)
Gain on cash flow hedge, net of taxes				133	133
Unrealized gain (loss) on securities, net of taxes				281	281
Foreign currency translation, net of taxes				209	209
Dividends declared			(20,647)		(20,647)
Excess tax benefits for share- based payments		651			651
Three-for-two stock splits	7,428	(7,428)
Three-for-two stock splits (in shares)	74,274,000
Balance at Dec. 31, 2010	22,227		526,201	(9,533)	538,895
Balance (in shares) at Dec. 31, 2010	222,264,000
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for stock incentive plans, net	122	9,455			9,577
Stock issued for stock incentive plans, net (in shares)	1,218,000
Stock purchased and retired	(194)	(12,862)	(22,136)		(35,192)
Stock purchased and retired (in shares)	(1,936,000)
Net income			296,381		296,381
Pension adjustment, net of taxes				(3,048)	(3,048)
Gain on cash flow hedge, net of taxes				387	387
Unrealized gain (loss) on securities, net of taxes				(314)	(314)
Foreign currency translation, net of taxes				(138)	(138)
Dividends declared			(47,327)		(47,327)
Excess tax benefits for share- based payments		3,371			3,371
Three-for-two stock splits	(36)	36
Three-for-two stock splits (in shares)	(358,000)
Balance at Dec. 31, 2011	22,119		753,119	(12,646)	762,592
Balance (in shares) at Dec. 31, 2011	221,188,000				221,187,660
Increase (Decrease) in Stockholders' Equity [Roll Forward]
Stock issued for stock incentive plans, net	152	11,105			11,257
Stock issued for stock incentive plans, net (in shares)	1,530,000
Stock purchased and retired	(201)	(13,885)	(16,515)		(30,601)
Stock purchased and retired (in shares)	(2,011,000)
Increased ownership interest in subsidiary, net of taxes			(5,507)		(5,507)
Net income			274,436		274,436
Pension adjustment, net of taxes				(1,707)	(1,707)
Unrealized gain (loss) on securities, net of taxes				(158)	(158)
Foreign currency translation, net of taxes				265	265
Dividends declared			(114,069)		(114,069)
Excess tax benefits for share- based payments		2,724			2,724
Three-for-two stock splits	(56)	56
Three-for-two stock splits (in shares)	(563,000)
Balance at Dec. 31, 2012	$ 22,014		$ 891,464	$ (14,246)	$ 899,232
Balance (in shares) at Dec. 31, 2012	220,144,000				220,144,287